Snap acting device



Jan. 31, 1933.

J. A. SPENCER SNAP ACTING DEVI-CE Filed Feb. 16 1931 2 Sheets-Sheet l'1933- v J. A. SPENCER 1,895,591

SNAP ACTING DEVICE Fileq Feb. 16, 1931 2 Sheet$-Sheet 2 Patented Jan..31, 1933 UNITED STATES PATENT OFFICE JOHN A. SPENCER, OF NEWTONVILLE,MASSACHUSETTS, ASSIGNOR TO GENERAL PLATE COMPANY, OF ATTLEBOEO,HASSACHUSETTB, A CORPORATION OF MASSACHUSETTS SNAP- nc'rmennwcnApplication filed February 16, 1931. Serial in. 516,042.

. This invention relates tosnap-acting devices, and with regard tocertain more specific features, to snap-actlng,,or overcentermg devices,particularly thermostats compose preferably of composite metal. 1

may be noted the provision of a snap-acting device which has anincreased amount of displacement between its two positions; asnapvalves, electrical switches, etc.; and the prov visionoi' a deviceof the class described which is economical in manufacture and s1m lo andpositive in action. Other objects wi 1 be part obvious and in partpointed -outhere.-'-

inafter.

tures of construction and arran ements of parts which will beexemplified in the structure hereinafter described, and the scope of theapplication of which willbe indicated in the following claims.

in the accompanying drawings, in which are illustrated several ofvarious possible embodiments of the invention,

Fig. 1 is a plan view of a snap-acting device embodying the invention;

Fig. 2 is a side elevation of'the device shown in Fig. 1; Fig. 3 is asectional view illustrating diagrammatically the method of forming thepresent invention;

Fig. 4 is a cross section taken substantially of thermostat 1Sfrequently termed bimetalon line 4-4 of Fig. 1;

Fig. 5 is a cross section showing a method of fixedly mounting thesnap-acting device of the present invention;

Fig. 6 is a cross section similar to Fig. 5 showing a. method ofadjustably mounting V device. The invention accordingly comprises'the;elements and combinations of elements,'fea'- the snapcting device of thepresent invention; and,

Fig. 7 is a plan view of a device embodying the invention and carryingelectrical coni g tacting means thereon. Among the several objects ofthe invention of resilient material is present inthe region wheredisplacements take place under change from one to another position. iThe present invention comprises an improvement over the nadiallycorrugated device illustrated in said copending application.

T he invention will be described principally by reference to itsthermostatic embodiment, that is, where it performs in response totemperature changes. However, it will be understood that, even as athermostat, the invention fundamentally a snap-acting Referring now moreparticularly to Fig. 1,

thereis illustrated at numeral 1, the interior,

dished or cup or concave radially corrugated region comprising theoperative portion of a thermostatic embodiment of the present invention.This portion 1 is preferably formed from a seamless cylinder ofcomposite thermostatic metal in the manner set forth in said copendingapplication, which comprises, briefly, longitudinally corrugating acylinder of thermostatic metal and constricting said corrugated cylinderat one end as well as compressing it longitudinally until substantiallya truncated cone or dished disc is obtained.

The term composite thermostatic metall coefiicients of thermalexpansion. This type lie. The principle upon which the thermostatoperates is that, undervarying conditions of hot and cold, one layer ofthe com layer, and thereby build up a stress in the body which the twometals form.

The stress thus set up grows with increased temperature until strainsare effected whereby the disc reverses curvature with a snap. That is,if the disc or dish or the like was originally concave, relative to itsoriginal confirmation it becomes convex, or vice versa.

The radial corrugations in the present device, as in the snap-actingdevice of said copending application, are advantageous in that theyprovide an increased amount of thermostatic metal in the central portionof said disc,

and, when the thermostat is brought to a condition in which it is aboutto snap, it effects an increase in the amount of displacement throughwhich the center of the thermostat operates. This increased displacementis highly advantageous whenthe thermostat is utilized, for example, inelectrical equipment, for making and breaking electrical contacts (seeFig. 7).

The present invention comprises the formation of a radially corrugateddisc such as illustrated in my copending application, and the provisionthereon of a substantially fiat, or uncorrugated rim or circumferentialportion 3. The rim is concentric with the resultin opening in the disc,said opening being su stantially at the focus of the radial arrangementof corrugations. A thermostat produced according to the presentinvention has the following advantages:

First, the inherent tendency of the thermostat to ex and radiall andthereby to decrease its kinematice ciency, is limited and controlled bythe relatively non-expansible rim or confining portion 3. That is, withthermostats of the type shown in said copending application, there isa.tendency u n heating for straightening of the sinuous e ge,

' with the result that the constrictive function cordingly better servesas a restricting or con-. fining or binding means for the remainder ofthe thermostat. That is to say, there are no undulations in theperiphery to provide resiliency. i

Second. the flat rim 3 provides more adequate facility for mounting saidthermostat, as for example, in an annular groove 15 in I an abuttingmember 17 (see Figf), for the reason that the rim 3 need not originallyformed with any sinubus curvature, and accordingly need notsubstantially change its shape as the thermostat changes from hot tocold position. Further, it is inherently more simple to hold a fiatsurface than to hold a corrugated surface.

sure of said copending application, as iilus trated diagrammatically inFig. 3. In Fig.

3, numeral 5 represents a radially corrugated thermostat of the generaltype shown in said copending application. In order to form thethermostat of the present invention, the thermostat 5 is-placed in apress 7, which has an interior annular shoulder 9 formed therein. Theannular shoulder 9 is sufficient in size to accommodate the thermostat5, and extends radially inward to the extent determined by the desiredwidth of the flattened rim portion 3.

Movably received in the press 7 is a die 11 having a depending annularflange 13, the width of which is substantially the same as the width ofthe shoulder 9 desired.

It will be seen that by bringing the portion 11 down upon the press 7,with a thermostat 5 therein, in such manner that compression is effectedbetween the flange 17 and the shoul-' der 9, that the edge of thethermostat 5 is compressed and swaged to secure the flattened rimportion 3, as desired.

It will be seen that the rim portion 3 may be madeof any suitabledimensions to effect the desired result.

Fig. 5, as has been indicated, illustrates a means for clamping orholding the rim 3 in a roove 15 of an abutment member 17, in a 'xedmanner. This Fig. 5 form of mounting is advantageous in cases where thethermostat is inoperative withina definite tem perature range and noadjustment of such range is necessary. When adjustment of thetemperature range of operation is desirable, a mounting of the generaltype shown in Fig. 6 is advantageously utilized. In Fig. 6, adjustmentis secured by threading a collar 19 into a threaded cap portion 21. Theportions 19 and 21 carry, respectively, concentric beads or ridges 23and 25, between which the rim 3 of the thermostat is secured. It: willbe seen that by threading the portions 19 and 21-t0gether, the beads 23and 25 exert a tripping pressure on the thermostat, thereby tending toincrease or decrease the concavity of said thermostat to a greater orless extent, and thereby regulating the temperature differential andtemperature range atwhich the thermostat operates or snaps.

Fig. 7 illustrates an embodiment of the present invention particularlyadapted for use with electrical apparatus. that the rim portion 3 hasbeen formed sufficiently wide to carry thereon one or more contactingbuttons or the like 27, which serve, in

suitable mountings, to make and break electrical contacts with theoperation of the ther mostat.

- It will be apparent that the present invention has many other uses andapplications.

It will be seen much more constrictive in its action.

For example, the substantially flat rim or edge of the present inventionpermits its use in valves, where it can be positioned to close a valveseat and effect a quick stopping of flow. Other uses will also beapparent.

It is to be understood that I am aware that a substantially flat rim hasa slight capacity to stretch but it isto be noted that such capacity ismuchless than the corresponding capacity in anqundulatory or sinuousrim. In the case of tlqge flat rim the stretch effects only a tensile stless, whereas in the undulatory rim a bending movement is eifectivef Myimprovement} comprises arranging the metal in the periphery so that itis not subjected to bending movements and hence is Hence the improvedincreased'speed attained in the snap action. It is to be understood thatthe invention refers to binding rims of the class set forth or analogousones performing the same functions.

If the invention is to be employed as a simple mechanical snap-acting orovercentering device, or spring, it will readily be seen that the use ofcomposite thermostatic metal is unnecessary, although possible. In suchinstances, a sheet of single resilient metal may be used with success.The action of the device as an overcentering element needs no furtherdescription, as it varies from the thermostatic element only in thatapplied ex-- ternal forces replace the self-engendered thermostaticforces in effecting the change of shape desired.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made incarrying out the above constructionswithout departing from the scope of the invention, it is fiat,uncorrugated region at the periphery of said disc.

2. A thermostatic unit comprising a. radially corrugated sheet ofcomposite thermostatic material, said sheet being provided With aconfining rim of uncorrugated mate rial.

3. A thermostatic unit comprising a cupped disc of bimetallic materialhaving substantially radial corrugations therein, said disc beingadapted to assume a position of opposite curvature under influence oftemperature variations, and a confining portion at the periphery of saidsheet, said portion being integral with the unit.

. A thermostat comprising a sheet of composite thermostatic metal,corrugations therein and means for confining expansion laterally of saidcorrugations. x

5. A thermostat comprising a sheet of composite thermostatic metal,corrugations thereerally of said corrugations comprising at least oneportion positioned counter to the corrugations, said corrugations beingradially arranged, said portion being circularly arranged and'said sheethaving an opening therein.

8. thermostat comprisinga sheet of com-- positethermostatic metal,corrugations therei in and meansfor confining expansion laterally ofsaid corrugations comprising at least one portion positioned counter tothe corrugations, sa d corrugatlons being radially arranged and saidportion being circularly arranged at the periphery of said sheet, thesheet having an opening therein substantially concentric with saidportion and substantially at the focus of said radial arrangement.

9. In combination, a thermostat and a mounting therefor, said thermostatcomprising a sheet of co iposite thermostatic metal having substantiallyradial corrugations therein and aportion free of said corrugatronsconfinmgsald corrugations, said mounting having a groove therein, andsaid portion cooperating with said groove.

10. In combination, a thermostat and a mounting therefor, saidthermostat comprising a sheet of composite thermostatic metal 1 havingcorrugations thereinand a portion free of said corrugations confiningsaid corrugations, said mounting comprising adj ustable mea-nsengagingsaid confining portion and adapted to apply varying strains thereto.

11. In combination, a thermostat and a mounting therefor, saidthermostat comprising a sheet of composite thermostatic metal havingcorrugations therein and a portion free of said corrugations confiningsaid corrugations, said mounting comprising adjustable'members, andconcentric beads on said adjustable members engaging said confiningportion and adapted to apply varying strains thereto.

able fulcrum adapted to support the thermostat at said peripheralportion.

15. A snap-acting device comprising a disc of resilient material havingradial corrugations therein, the plane of the central portion of saiddisc being displaced from the plane of the peripheral portion thereof,and

means confining expansion laterally of said corrugations comprisingmeans positioned counter to said corrugations at the periphery of saiddisc, the said disc. being suitably resilient, whereby upon suitableactuation thereof, 1t overcenters to assume apositlon of oppositeconfiguration.

16. A snap-acting device comprising a disc of resilient material havingradial corruga tions therein, the plane of the central portion of saiddisc being displaced from the plane of the peripheral ortion thereof,and meansconfining expansion laterally of said corrugations comprisingmeans positioned counter to said corrugations at the periphery of saiddisc, thesaid disc being suitably resilient, whereby upon suitableactuation thereof, it overcenters to assume a position of op ositeconfiguration, said confining means eing integral with the disc itself.

17 A snap-actingdevice comprising a disc of resilient material havingradial corrugations therein, the plane of thelcentral portion of saiddisc being displaced from the plane of the peripheral portion thereof,and an uncorrugated peripheral region on said disc, the said disc beingsuitably resilient, whereby upon suitable actuation thereof, itovercenters to assume a position of opposite config uration.

In testimony whereof, I have signed my name to this specification this,30th day of January,'1931. L a

JOHN A. SPENCER.

